public class BinarySearchTree {
    static class TreeNode{
        int val;
        TreeNode left;
        TreeNode right;
        public TreeNode(int val){
            this.val = val;
        }
    }
    public TreeNode root;
    public  boolean search(int val){
        if(root == null) return false;
        TreeNode cur = root;
        while(cur != null){
            if(cur.val < val){
                cur = cur.right;
            }else if(cur.val > val){
                cur = cur.left;
            }else{
                return true;
            }
        }
        return false;
    }

    public boolean insert(int val){
        TreeNode node = new TreeNode(val);
        if(root == null){
            root = node;
            return true;
        }
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null){
            if(cur.val < val){
                parent = cur;
                cur = cur.right;
            }else if(cur.val > val){
                parent = cur;
                cur = cur.left;
            }else{
                return false;
            }
        }
        if(parent.val < val){
            parent.right = node;
        }else{
            parent.left = node;
        }
        return true;
    }
    public void remove(int val){
        if(root == null){
            System.out.println("树为空");
            return;
        }
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null){
            if(cur.val < val){
                parent = cur;
                cur = cur.right;
            }else if(cur.val > val){
                parent = cur;
                cur = cur.left;
            }else{
                removeNode(parent, cur);
                return;
            }
        }

    }
    private void removeNode(TreeNode parent, TreeNode cur){
        if(cur.left == null){
            if(cur == root){
                root = root.right;
            }else if(cur == parent.left){
                parent.left = cur.right;
            }else{
                parent.right = cur.right;
            }
        }else if(cur.right == null){
            if(cur == root){
                root = root.left;
            }else if(cur == parent.left){
                parent.left = cur.left;
            }else{
                parent.right = cur.left;
            }
        }else{
            TreeNode target = cur.right;
            TreeNode targetParent = cur;
            while(target.left != null){
                targetParent = target;
                target = target.left;
            }
            if(targetParent.left == target){
                targetParent.left = target.right;
            }else{
                targetParent.right = target.right;
            }

        }
    }
}
